Plastic has taken the place of other materials in a variety of industries. In the packaging industry, plastic has replaced glass to minimize breakage, reduce weight, and reduce energy consumed in manufacturing and transport. In other industries, plastic has replaced metal to minimize corrosion, reduce weight, and provide color-in-bulk products.
Recently, plastic has begun to replace wood in building materials where the wood is susceptible to rotting, warping, or discoloration. The advent of thermoplastic biofiber composites has made outdoor decks, porches, railings and stairways more durable. With structural issues resolved, the next key factor is making the plastic composite look like naturally-colored or stained wood.
Much like any assembly line, modules of ingredients come together at a final article formation station. For example, an extruder for deck planks might have as ingredients the thermoplastic resin, wood fiber or wood flour, and one or more “masterbatches” of additives.
These masterbatches are mixtures of a plastic resin and specialized, expensive additives, with the resin serving as a carrier for the additive. The most common specialized, expensive additive is colorant.
Pellet-based concentrates for colorant applications have be used at high dilution or “letdown” ratios to achieve good color distribution.
As with any modern manufacturing facility, production runs of thermoplastic composites made into final articles need to be very efficient. In the scale-up of production runs for one quantity of final product, the amount and choice of ingredients in the colorant concentrate can be quite different from the amount and choice of ingredients in the colorant concentrate for production runs for a different quantity of that same product. In other words, no two colorant concentrates are likely to be the same, because of the need to match color precisely, but there are significant issues in attempting to mix a colorant concentrate into a thermoplastic biofiber compound to make simulated wood products.